4. • The accidental discovery of Penicillin from the fungus
Penicillium notatum was capable of killing a wide range
of harmful bacteria such as Streptococcus ,
Meningococcus and Diphtheria.• However contrary to what the US Surgeon William H
Steward , reported in 1967 “….that we had essentially
defeated infectious diseases and could close the book of
them….”, the golden era did not even last for half a
century.• The Infectious Disease Society of America (IDSA)
reported that the majority of bacterial pathogens that
cause fatal infections are likely to be resistant to at least
one of the drugs, so we experience an increased
concern in worldwide public health because of
emergence of antibiotic resistant pathogens.• So, there is an urgent need for new antimicrobial agents
and new strategies to overcome problematic resistant
pathogens.
5. HOW RESISTANCE?
Bacteria employ different strategies to resist
antibiotics:
• Spontaneous mutation in the gene encoding the
target protein.
• Transfer of antibiotic resistant genes from other
bacteria.
Hence there is an urgent need to develop novel
classes of potent antibacterial agents with new
inhibitory mechanisms, to compact problematic
pathogens and their antibiotic resistant derivatives.
6. STRATEGIES TO COMPACT
RESISTANT PATHOGENS
Proper education of physicians regarding
relationship between antibiotic resistance and
improper use of antibiotics.
Appropriate prescribing of antibiotics and use of
specific diagnostic test to differentiate between
bacterial and viral infections.
Hygiene of the hospitals and working
environments.
Public awareness of the negative consequences
of antibiotic resistance and shortage of effective
anti-infective agents.
A desirable approach is the use of Anti-Microbial
Peptides (AMPs) from bacteria –
7. WHAT ARE
BACTERIOCINS?
Bacteriocins are proteinaceous or peptidic toxins
produced by bacteria to inhibit the growth of
similar or closely related bacterial strains.
They have low molecular weight rarely over 10kD
Undergo post translational modifications.
They are cationic and amphipathic molecules.
8. DIFFERENCES
BACTERIOCINS ANTIBIOTICS
• Narrow spectrum
activity.
• Ribosomally
synthesized.
• Are non-toxic.
• Have no side effects.
• Broad spectrum
activity.
• Usually are secondary
metabolites.
• Are toxic.
• Exhibit side effects.
9. MICROBIAL ORIGIN
1. Bacteriocins of Eukarya
• Eukaryotic AMPs contribute to innate immunity and is
part of the first defense line against harmful
microorganisms.
• Micro molar concentrations are only required for their
activity when compared to bacterial AMPs which
require Pico to Nano molar concentrations.SL.No Antimicrobial Peptides
(AMPs)
Source
1. Histatins Human saliva
2. Defensins Mammalian
neutrophils
3. Trichorzins Trichoderma
4. Mellitin Bee venom
10. 2. Bacteriocins of Archaea
• Archaea synthesize bacteriocin like AMPs named
archaeocins.
• The Halocin S8 from halobacteria is the first
discovered archaeocin.
3. Bacteriocins of Gram negative bacteria
• Bacteriocins are initially isolated from Gram negative
bacteria.
• The first discovered bacteriocin was Colicin from
E.coli by Gratia in 1925.SL.N
o
Organism Bacteriocin
1. Klebsiella pneumonia Klebicins
2. Pseudomonas Pyocins
3. Hafnia alvei Alveicins
11. COLICINS
• Colicins are proteins produced by some strains of
Escherichia coli that are lethal for related strains
of E.coli.
• Colicin peptides are plasmid encoded.
Structure
12. 4. Bacteriocins of Gram positive bacteria
• Bacteriocins are also produced by a number of
gram positive bacteria.
• The most important among them is the Lactic
Acid Bacteria (LAB), which produce a wide range
of potent and useful bacteriocins.
• The most important among them is Nisin.
SL.N
o
Organism Bacteriocin
1. Lactococcus lactis Nisin A
2. Streptococcus uberis Nisin U
3. Streptococcus salivarius Salivaricin A
13. NISIN
• Nisin is a polycyclic antibacterial peptide
produces by Lactococcus lactis that is used as
food preservative.
14. BIOSYNTHESIS
• Bacteriocins are ribosomally synthesized and the
genes necessary for their production and
immunity are usually arranged as operons.
• These operons can be located on conjugative
transposable elements , on plasmids etc.
Biosynthesis of Nisin
• The genes involved in the biosynthesis of nisin
are located on a 70 kb conjugative transposon.
• It is encoded by a cluster of 11 genes-nis A, nis B,
nis T, nis C, nis I, nis P, nis R, nis K, nis F, nis E,
nis G.
16. CLASSIFICATION(gram positive
bacteria)
1. Class I
• Also called as lantibiotics.
• Undergo post translational modifications.
• Nisin is the most well known example.
• The varients of nisin are nisin A, nisin Z, nisin U etc..
2. Class II
• Simpler than lantibiotics.
• Do not have post translational modifications.
• Divided into 3 subclasses:
i) Class II -A
ii) Class II-B
iii) Class II-C
3. Class III
• Have complex activity and protein structure.
19. BACTERIOCIN DETECTION
AND QUANTIFICATION
METHODS
1. Biological tests
• Most commonly used bioassays are Agar diffusion
test and Turbidometric methods.
2. Genetic tests
• Polymerase Chain Reaction(PCR) or Southern
Blotting are genetic test that can determine if a
bacterial strain has the genetic potential to encode a
specific bacteriocin.
3. Immunological tests
• Method of choice for detecting and quantifying
bacteriocins.
• Based on antigen-antibody reaction.
24. 3.Application of bacteriocin in medicine
SL.N
o
Group of bacteriocins Pharmaceutical
applications
1.
Lantibiotics
Blood pressure treatment,
inflammation and allergy
treatment, skin infection
treatment, mastitis
infection treatment, dental
carries treatment.
2.
Colicins
Hemolytic uremia
syndrome treatment,
urogenital infection
treatment, hemorrhagic
colitis treatment
3. Microcins Salmonellosis treatment.
25. ADVANTAGES
DISADVANTAGES
• Easy to find.
• Highly specific.
• Low MIC.
• Little to no toxicity to
human cells.
• No allergic reactions.
• Active against dividing
and non dividing cells.
• Ease of genetic
manipulation and
production.
• Reduced resistance
levels.`
• High cost for
production of purified
bacteriocin.
• Instability in biological
matrices(extreme pH,
salt).
• Narrow range of
activity.
• Consumer
acceptance
challenges.
26. OVERCOMING THE
CHALLENGES
1. Hurdle technology
Hurdle technology refers to the intelligent combination of
hurdles to secure safety, nutritive and economic aspects of
food product.
EXAMPLES:
1. Calderon-Miranda et al investigated the use of Pulse
Electric Field (PEF) and nisin in combination to
inactivate Listeria innocua in skim milk. The results
showed an additive effect on the inactivation of L.
innocua when the pathogen was exposed to PEF and
the sensitized cells treated with nisin.
2. Nilsson et al investigated the combined action of nisin
and carbon dioxide on Listeria monocytogens cells.
Nisin brought about a two log reduction in the wild type
Listeria monocytogens cells and acted synergistically
with carbon dioxide to give a four log reduction in cell
27.
28. 2. Antimicrobial packaging film
• The aim of antimicrobial packaging is to reduce,
inhibit or retard the growth of microorganisms in
the packaged food or packaging material itself.
• Based on the amphiphilic nature bacteriocins
have successfully coated on to packaging
material, hence prevent microbial growth on food
surface.
EXAMPLES:
1. Nisaplin containing cellophane based coatings
for controlling total aerobic bacteria in chopped
meat.
29.
30.
31. 3. Microencapsulation
Microencapsulation is another method to deliver
antimicrobial agents such as nisin into food
systems.
EXAMPLES:
1. Benech et al, reported that nearly 90%of the
nisin activity was retained in cheese made with
encapsulated nisin Z liposomes after 6 months
compare to 12% of the nisin activity in cheese
made with nisin producing starter.
32.
33. CONCLUSION AND FUTURE
PERSPECTIVE
• The alarming increase in antibiotic resistant
bacterial infections is a serious threat to humans
and animals worldwide.
• In this respect AMPs such as bacteriocins are
promising therapeutic tools because of their rapid
and specific killing activity against pathogens.
• Studies to extend the detailed understanding on
how AMPs function in medical settings, how their
mode of action, toxicity and immunogenicity are
carried out in humans will be crucial for the further
development of bacteriocins into particular use in
medicine.
